I would put my money on the Banana peel being the culprit...fruit has been sprayed with pesticides and unless you rinsed it off REAL well, those pesticides would leak into the water, and depending on what was used, even a good rinse wouldn't do it. As CC said, you need to build the infusoria culture in another container. I personally use Java Moss from an established tank to make my cultures, that way no chance of some pesticide getting into the water.
I also would give the male some time to rest...he'll need to be reconditioned as he won't have eaten during the time he was with the female and caring for the fry (unless you fed him, but most males won't eat anyway). And he'll also be tired, all that embracing is exhausting work for the male, then the care of the eggs, he hasn't had a chance to rest up.
Linda